Method for manufacturing semiconductor device

ABSTRACT

A method for manufacturing a semiconductor device includes forming a recess with a device separating film and a first hard mask layer so that a pad nitride film for defining a recess gate region may remain with a conventional mask. The method additionally the recess gate region to facilitate a subsequent process for etching a gate electrode without a step difference between the device separating film.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. patent application Ser. No. 11/529,540, filed on Sept. 29, 2006, which claims priority to Korean patent application number 10-2006-0027005, filed on Mar. 20, 2006, which are incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention generally relates to a method for manufacturing a semiconductor device, and more specifically, to a technology of etching a semiconductor substrate with a first recess gate for defining a recess gate region as a mask in formation of a recess gate, thereby preventing generation of a height difference from the semiconductor substrate because a device separating film except the recess gate region is etched due to an etching selectivity.

As a channel length of a cell transistor is decreased, an ion concentration of a cell channel is increased to adjust a threshold voltage of the cell transistor. As a result, an electric field of source/drain regions is increased and leakage current is increased so that a refresh characteristic of a DRAM is degraded.

FIG. 1 is a layout diagram illustrating a conventional semiconductor device to increase the channel length of the cell transistor.

The conventional semiconductor device of FIG. 1 includes an active region 1, a recess gate region 2 and a gate region 3.

The linewidth of the recess gate region 2 is shown to be narrower by 2D than that of the gate region 3. The width between the gate regions 3 is shown to be F.

FIGS. 2 a through 2 f are diagrams illustrating a conventional process for manufacturing a semiconductor device. FIGS. 2 a(i) through 2 f(i) are cross-sectional diagrams taken along the line I-I′ of FIG. 1, and FIGS. 2 a(ii) through 2 f(ii) are cross-sectional diagrams taken along the line II-II′ of FIG. 1.

A device separating film 50 is formed over a semiconductor substrate 10 including a pad oxide film 13 and a pad nitride film 15.

After the pad nitride film 15 is removed, ions are implanted into the resulting structure to form well and channel ion-implanting regions (not shown). Then, a polysilicon layer 45 is formed over the resulting structure.

The polysilicon layer 45 and the pad oxide film 13 are etched with the first gate mask (not shown) which defines a recess gate region as an etching mask to form a polysilicon pattern 45 and a pad oxide pattern 13 a which define the recess gate region 2 of FIG. 1.

The semiconductor substrate 10 of the recess gate region 2 of FIG. 1 is etched at a predetermined thickness to form a recess 53. Here, the polysilicon pattern 45 a is simultaneously removed when the recess 53 is formed. The semiconductor substrate 10 adjacent to the device separating film 50 has a relatively slower etching speed to cause a silicon horn.

A gate insulating film 60 is formed over the exposed semiconductor substrate 10. Then, a gate conductive layer 65 for filling the recess 53 is formed, and a hard mask layer 90 is formed thereon. The gate conductive layer 65 has a deposition structure including a bottom electrode 70 and a top electrode 80.

The hard mask layer 90 and the gate conductive layer 65 are patterned with a second gate mask (not shown) for defining a gate as an etching mask to form a gate 99.

A thickness difference of bottom electrodes over the gate insulating film 60 and the device separating film makes the surface of the device separating film 50 lower than that of the silicon substrate, and causes the bottom electrode 75 of the gate formed over the silicon substrate which is an active region to be over-etched in order to etch the thick bottom electrode of the device separating film. Also, the conventional method for manufacturing a semiconductor device increases word line capacitance after the gate is formed, and degrades the operating speed of the DRAM and a refresh characteristic of the semiconductor device resulting from increase of leakage current.

SUMMARY OF THE INVENTION

Various embodiments are directed at a method for manufacturing a semiconductor device including forming a recess with a device separating film and a first hard mask layer so that a pad nitride film for defining a recess gate region may remain with a conventional mask. The method additionally defines the recess gate region to facilitate a subsequent process for etching a gate electrode without a step difference between the device separating film and a semiconductor substrate and to improve a refresh characteristic of the device.

According to an embodiment of the present invention, a method for manufacturing a semiconductor device comprises:

forming a deposition structure including a pad oxide film and a pad nitride film which expose a device separating region of a semiconductor substrate;

etching the semiconductor substrate with the pad oxide film and the pad nitride film as an etching mask to form a trench which defines an active region;

forming an insulating film for separating the device which fills the trench and planarizing the insulating film until the pad nitride film is exposed to form a device separating film;

etching the pad nitride film and the device separating film by an exposing and etching process with a first gate mask which defines a line-type recess gate region to expose the pad oxide film except the recess gate region;

forming a first hard mask layer which fills the exposed region;

removing the residual pad nitride film and pad oxide film with the first hard mask layer and the device separating film as an etching mask to expose the semiconductor substrate of the recess gate region;

etching the exposed semiconductor substrate at a predetermined thickness to form a recess;

removing the first hard mask layer and the pad oxide film to form a gate oxide film over the exposed semiconductor substrate;

forming a gate conductive layer for filling the recess over the resulting structure;

forming a gate hard mask layer over the gate conductive layer; and

patterning the gate hard mask layer and the gate conductive layer with a second gate mask for defining a gate as an etching mask to form a gate.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:

FIG. 1 is a layout diagram illustrating a conventional semiconductor device;

FIGS. 2 a through 2 f are diagrams illustrating a conventional process for manufacturing a semiconductor device;

FIG. 3 is a layout diagram illustrating a semiconductor device according to an embodiment of the present invention;

FIGS. 4 a through 4 f are diagrams illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention; and

FIGS. 5 a through 5 c are diagrams illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a layout diagram illustrating a semiconductor device according to an embodiment of the present invention.

In an embodiment, a semiconductor device includes an active region 101 defined by a device separating film 150, a recess gate region 102 and a gate region 103.

The linewidth of the recess gate region 102 is shown to be narrower by 2D than that of the gate region 103, and the width between the gate regions 103 is shown to be F.

FIGS. 4 a through 4 f are diagrams illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention. FIGS. 4 a(i) through 4 f(i) are cross-sectional diagrams taken along the line I-I′ of FIG. 3, and FIGS. 4 a(ii) through 4 f(ii) are cross-sectional diagrams taken along the line II-II′ of FIG. 3.

A pad oxide film 113 and a pad nitride film 115 which define the active region of FIG. 3 are formed over a semiconductor substrate 110. Then, the semiconductor substrate 110 is etched at a predetermined thickness with the pad oxide film 113 and the pad nitride film 115 to form a trench. Preferably, the thickness of the pad nitride film 115 ranges 50 to 200 nm.

Thereafter, a device separating oxide film (not shown) for filling the trench is formed, and a CMP process is performed until the pad nitride film 115 is exposed to planarize the device separating oxide film. As a result, a device separating film 150 is formed. Then, a well-channel-ion-implanting process is performed on the active region 101 of FIG. 3 defined by the device separating film.

After a photoresist film is formed over the resulting structure, the pad nitride film 115 and the device separating film 150 are etched by an exposing and etching process with a first gate mask (not shown) for defining the line-type recess gate region 102 to expose the pad oxide film 113 except for the recess gate region 102.

After the photoresist film is removed, the exposed region between pad nitride film patterns 115 a is filled with a first hard mask layer 145. Then, a CMP process is performed to planarize the first hard mask layer 145. The first hard mask layer 145 is selected from one of an oxide film, a SiON film, an amorphous carbon film, a silicon film and combinations thereof.

The pad nitride film patterns 115 a are removed by a wet-etching process with the hard mask layer 145 and the device separating film 150 as etching masks.

The pad oxide film 113 of the recess gate region is removed to expose the semiconductor substrate of the recess gate region. Here, the device separating film 150 and the first hard mask layer 145 are etched at a predetermined thickness so that the heights of the device separating film 150 and the first hard mask layer 145 are formed to be higher than that of the semiconductor substrate.

The exposed semiconductor substrate 110 is etched at a predetermined thickness to form a recess 153. After, an oxide film (not shown) is formed over the semiconductor substrate 110 of the recess 153, a channel-ion-implanting process may be performed thereon.

The first hard mask layer 145 can be removed when the semiconductor substrate 110 is etched in FIG. 4 d. After the residual first hard mask layer 145 and pad oxide film 113 a are removed by a wet-etching process, a gate oxide film 160 is formed over the exposed semiconductor substrate 110.

A gate conductive layer 165 for filling the recess 153 is formed over the resulting structure, and a gate hard mask layer 190 is formed over the gate conductive layer 165. Preferably, the gate conductive layer 165 has a deposition structure including a bottom electrode 170 and a top electrode 180. The bottom electrode 170 is selected from one of n+ polysilicon, p+ polysilicon, TiN and combinations thereof. The top electrode 180 is selected from one of WN/W, WSix/WN/W, Ti/TiN/W, Ti/WN/W, TiN/Ti, TiN, and combinations thereof.

The gate hard mask layer 190 and the gate conductive layer 165 are patterned with a second gate mask (not shown) for defining a gate which is the gate region 103 of FIG. 3 as an etching mask to form a gate 199.

After the photoresist pattern is removed, ions are implanted with the gate 199 as an ion-implanting mask to form a LDD region (not shown) in the semiconductor substrate 110 between the gates 199. Then, a general process for manufacturing a transistor is performed which includes forming a gate sidewall insulating film, a source/drain region, a contact plug, a bit line contact and a bit line, a capacitor contact and a capacitor, and a metal line contact and a metal line, thereby obtaining a semiconductor device.

FIGS. 5 a through 5 c are diagrams illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention. FIGS. 5 a(i) through 5 c(i) are cross-sectional diagrams taken along the line I-I′ of FIG. 3, and FIGS. 5 a(ii) through 5 c(ii) are cross-sectional diagrams taken along the line II-II′ of FIG. 3.

First, the processes of FIGS. 4 a through 4 d are performed to form a recess.

A sidewall insulating film 245 a is formed at sidewalls of a pad oxide film 213 a, a first hard mask layer 245 and a first recess (not shown). The bottom semiconductor substrate 210 of the first recess (not shown) is isotropic-etched with the sidewall insulating film 245 a as a mask to form a second recess 255 whose bottom has a circular or elliptical bottom.

The first hard mask layer 245 and the pad oxide film 213 a are removed by a wet-etching process to form a gate oxide film 260 over the exposed semiconductor substrate 210.

A gate conductive layer 265 for filling the Second recess 255 is formed over the resulting structure. A gate hard mask layer 290 is formed over the gate conductive layer 265 which has a deposition structure including a bottom electrode 270 and a top electrode 280. The bottom electrode 270 is selected from one of n+ polysilicon, p+ polysilicon, TiN and combinations thereof. The top electrode 280 is selected from one of WN/W, WSix/WN/W,Ti/TiN/W, Ti/WN/W, TiN/Ti, TiN, and combinations thereof.

The gate hard mask layer 290 and the gate conductive layer 265 are patterned with a second gate mask (not shown) for defining a gate of the gate region 103 of FIG. 3 to form a gate 299.

After the photoresist pattern is removed, ions are implanted with the gate 299 as an ion-implanting mask to form a LDD region (not shown) in the semiconductor substrate 210 between the gates 299. Then, a general process for manufacturing a transistor is performed which includes forming a gate sidewall insulating film 295, a source/drain region, a contact plug, a bit line contact and a bit line, a capacitor contact and a capacitor, and a metal line contact and a metal line, thereby obtaining a semiconductor device.

As described above, according to an embodiment of the present invention, a method for manufacturing a semiconductor device including forming a recess with a device separating film and a first hard mask layer so that a pad nitride film for defining a recess gate region may remain with a conventional mask for defining the recess gate region to facilitate a process for etching a gate electrode, to reduce word line capacitance and leakage current of a charge storage voltage.

The foregoing description of various embodiments of the invention has been presented for purposes of illustrating and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. Thus, the embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. 

1. A method for manufacturing a semiconductor device, the method comprising: forming a pad oxide film and a pad nitride film over a semiconductor substrate; etching the semiconductor substrate with the pad oxide and nitride films as an etching mask to form a trench that defines an active region; filling the trench with an insulating film and planarizing the insulating film; etching the pad nitride film and the insulating film, wherein a region the pad oxide film that does not include a recess gate region is exposed; forming a first hard mask layer over the exposed region of the pad oxide film; removing the residual pad nitride film and etching the pad oxide film with the first hard mask layer and the insulating film as an etching mask to expose the semiconductor substrate of the recess gate region; etching the exposed semiconductor substrate at a predetermined thickness to form a first recess; forming a sidewall insulating film over a sidewall of the pad oxide film, the first hard mask layer, and the first recess; isotropic-etching the bottom semiconductor substrate of the first recess with the sidewall insulating film as a mask to form a resulting structure including a second recess having a circular or elliptical shape; removing the first hard mask layer and the pad oxide film to form a gate oxide film over the exposed semiconductor substrate; forming a gate conductive layer over the resulting structure that fills the second recess; forming a gate hard mask layer over the gate conductive layer; and patterning the gate hard mask layer and the gate conductive layer with a gate etching mask to form a gate.
 2. The method according to claim 1, wherein the thickness of the pad nitride film ranges from 50 to 200 nm.
 3. The method according to claim 1, wherein a well-channel-ion-implanting process is performed on the active region after the insulating film is formed.
 4. The method according to claim 1, wherein the first hard mask layer is selected from one of an oxide film, a SiON film, and amorphous carbon film, a silicon film and combinations thereof.
 5. The method according to claim 1, wherein said removing the residual pad nitride film, said etching the pad oxide film, and said etching the semiconductor substrate to form a first recess includes a wet-etching process using the first hard mask pattern and the device separating film as an etching mask.
 6. The method according to claim 1, wherein a channel-ion-implanting is performed after the second recess is formed and an oxide film is formed over the semiconductor substrate.
 7. The method according to claim 1, wherein said removing the first hard mask layer and the pad oxide film includes performing a wet-etching process.
 8. The method according to claim 1, wherein the gate conductive layer has a deposition structure including a bottom electrode and a top electrode.
 9. The method according to claim 8, wherein the bottom electrode is selected from one of n+ polysilicon, p+ polysilicon, TIN and combinations thereof.
 10. The method according to claim 8, wherein the top electrode is selected from one of WN/W, WSix/WN/W, Ti/TiN/W, Ti/WN/W, TiN/Ti, TIN and combinations thereof.
 11. The method according to claim 1, further including implanting ions using the gate as an ion-implanting mask to form a LDD region.
 12. The method according to claim 1, wherein pianarizing of the insulating film is performed by a CMP process until the pad nitride film is exposed. 